Add Casino Engine to CQRS Samples

[nekzabirov]

Summary

Adds nekzabirov/IGaming-Game-Engine to docs/cqrs.md → Samples.

Why this fits the CQRS section

Casino Engine is a production-grade open-source iGaming/casino engine in Kotlin/Ktor with a real CQRS bus implementation:

• `ICommand` / `IQuery` interfaces; commands return `Result` (wrapped in `runCatching`), queries return `R` directly
• Handlers register as Koin beans with a marker `bind CqrsHandler::class`; `BusImpl` calls `getAll()` and resolves the generic type argument with Kotlin reflection — adding a new handler is one Koin line, the bus module never changes
• Polymorphic handler resolution: a handler `SetImageCommandHandler : ICommandHandler<SetImageCommand, Unit>` automatically serves concrete subtypes via class-hierarchy walk
• Read-side view types are top-level data classes co-located with their query files (`CollectionView` next to `FindCollectionQuery.kt`) — no separate `projection/` package

The current samples section is .NET-heavy; this adds a non-trivial Kotlin/Ktor CQRS reference.

Production-tested on moonbet.casino and 2k.ua. Apache 2.0.

Checklist

• Separate PR for this category (hexagonal-architecture is a separate PR)
• Format matches: `user/repo - Description`
• Meaningful description